The manufacture at low cost of large surface exchangers is essential to save energy by allowing increased heat recovery.
The conventional exchangers are of the tube and calender type. One of the fluids taking part to the exchange is passed through the tubes, while the other fluid taking part in the exchange is circulated around the tubes in the calendar. The exchange surface per unit volume, also called the specific surface, which can be obtained with such exchangers is usually low. As a matter of fact, for constructional reasons, it is not easy to reduce the diameter of the tubes and the distance or spacing between the tubes to less than 1 cm.
The plate exchangers can be used to obtain larger exchange specific surfaces. In these exchangers, the fluids taking part in the exchange circulate on each side of the plates. However, the specific surface in this type exchanger is also limited because the distance between the plates cannot be reduced too much.
Other prior art heat exchangers are known which consist of stacked perforated sheets, joined so as to obtain channels, by superposition of the perforations, with a relatively hot fluid being passed through certain ones of the channels, and a relatively cold fluid through other channels. Heat is transferred from channel to channel by conduction through the material forming at least one part of said sheets.